- MATEC Web of Conferences
MATEC Web of Conferences 78, 01005 (2016)
DOI: 10.1051/ matecconf/2016 7801005
IConGDM 2016
Optimum Design for Multi-angle Kitchen Grater
Mechanism for Biodegrading Kitchen Waste
Zol Bahri Razali1,*, Abdul Rahim Abdul Hasim1 , and Mohd Hisam Daud1
1
Robotics and Automation Technology, Faculty of Engineering Technology, Universiti Malaysia
Perlis, 02100 Padang Besar, Perlis, Malaysia
Abstract. The study presented in this report is regarding on the
conceptual design of the grater machine which meant to shred food wastes
into small and fine size particle. This study will focus on the waste
management factor of the food waste produced in the home kitchen. A
study is conducted to compare the most suitable material and geometric
shape of the grating blades by comparing with similar existing devices in
the market. The chosen material and blade design are to be evaluated for its
characteristics and performance by using the FEM method. The analysis is
taking all the constraints regarding the design as well as its advantages are
to be considered in designing a new grating blade for the optimum end
product making. This design derived through in the consideration for the
home application rather than domestic use. This brings the meaning that
the compact and small size design. With the detailed evaluation of the
stress reaction on the blades to provide the safety and sustainability factor
of the device as well as the people that is using the device.
1 Introduction
The “Grater” machine (also known as a shredder) is a kitchen utensil used to grate foods
into fine pieces [1]. This study will focus on the waste management factor of the food waste
produced in the home kitchen. The project is to analyse the optimum design of Multi-angle
Kitchen Waste Grater machine. For this intention, several types of existing grater blade
design in the market are to be evaluated for its characteristics. All the constraints regarding
the design as well as its advantages are to be considered in designing a new grating blade
for the optimum fineness end product and the speed of grating capacity. This design should
consider for the application in the house which mean it should be smaller size and the
safety precaution factor of the operator and other peoples in surrounding area must be
placed at the top priority.
The main objective is about the kitchen waste management where it is to be recycled
and reuse for the purpose of agriculture. Today’s growth of our country shows the rapid
increment of waste producing amount. The waste producing rate is 19,000 tons of garbage a
day and the number getting increase and estimated will approach 30,000 tons per day by
year 2020 [2]. This scenario has put a major constraint in managing the resources for the
landfill. The government has launched the Solid Waste Management Act and Public
*
Corresponding author: zolbahri@unimap.edu.my
© The Authors, published by EDP Sciences. This is an open access article distributed under the terms of
the Creative Commons Attribution License 4.0 (http://creativecommons.org/licenses/by/4.0/).
MATEC Web of Conferences 78, 01005 (2016)
DOI: 10.1051/ matecconf/2016 7801005
IConGDM 2016
Cleansing 2007 (Act672) which had been implemented since 1st September seen
tremendously a great effort to encourage the public in adopting recycling. Other developed
countries like the United States, Japan and most of the European countries has long been
practiced the recycling method to reduce the environmental loadings and natural resources
consumption [3]. It is the time where recycling practices of waste produced at home
become a new branch of an engineering equipment production to be explored in line with
current needs [4].
The analysis consists of mincing mechanism design force analysis and the simulation of
the grater. For this purpose, several samples of existing grater blades will be analysed. The
main focus is where it should begin by mean of analyse the design of grate mechanism
material and propose the new design which offer the improvement in the qualities and
durability. The mechanical properties of the food variants will be taken in consider for
determining the required strength of the greater material or the blades [5]. This includes
every scope of human consumption varies from organic based product such as vegetables
along with its wastes which have the lower hardness property for livestock material such as
meat and bones which are the hardest materials in human food classification.
2 Literature review
Utilizing or recycling the food waste materials have inspired the invention of a grater
machine to decomposition the kitchen waste to a suitable and fast dissolve to become
agricultural fertilizer. A good blade design to shreds the organic materials is important to
result a fine material for composting. It is also meant that the blade should also bear in
working with the varied types of waste ranging from plants to livestock products. The
market nowadays has many types of grater machine and this is just another innovation
which may vary the choices available.
The design analysis will be based on the varied approaches that designer used, and
using the thinking that have been arisen in design research. The logic will gives the lead in
describing the reasoning in design. A ‘sparse’ description which comes from logic will
opens the way to explore the variants of the design to be differ from other point of features
and advantages [2]. The reasoning patterns that usually used in problem solving of the a set
of unknowns and known are described as such equation:
WHAT
(Grater
machine)
HOW
(working
principle)
LEADS TO
DESIGN
(aspired)
Fig. 1. The transformation of the problem solving method with regards to the current situation
2.1 Basic concept of food grater.
The existing products of grater only concerning to the small application in the kitchen, for
cutting edges, used for grating cheese and other foods [5]. To expand the usage for home
application of handling food waste, the similar equipment used in certain huge applications
such as waste management center should be taken in consider. The grater machine should
have the high capacity rate of processing and must be able to withstand the greatest
hardness of the food material which are represented by the poultry products such as animal
bones.
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MATEC Web of Conferences 78, 01005 (2016)
DOI: 10.1051/ matecconf/2016 7801005
IConGDM 2016
2.2 Grater blades materials.
When handling with food based material, the best and most common material used is the
stainless steel. Referring to Table 1, stainless steel-430 type is commonly used for
applications such as equipment enclosures and housings. For cutting mechanism
applications, the hardened martensitic stainless steel-316 is likely chosen. The Stainless
Steel-316 is the one classified as the “Food Grade” type. Where the applications involve
with high temperatures, the non-hardened ferritic and austenitic types of stainless steel
which having the higher duplex strength is the most suitable to be used [6].
The material selection is crucial to avoid weaknesses in the design. In this case it does
majorly refer to the corrosion from being occur and the stand ability to what it purposed.
Better surface finish will influence the functional performance. It also makes the device
easy to clean, thus keeping away the risk of corrosion. The several types of stainless steel
usually used in food processing equipment is as shown below together with its typical
applications.
Table 1. Types of Stainless Steel and its typical applications
Type
420 (Martensitic)
430 (Ferritic)
304 (Austenitic)
316 (Austenitic)
14539
(Austenitic)
14662 (Duplex)
6%Mo.Types
(Austenitic)
Applications
Spatulas, Professional knives, Cooks, etc.
Moderately corrosive environment (e.g. dry foods, fruits, vegetables,
drinks, etc.), panel (i.e., components that require weldability or little
formability), table surfaces or cladding equipments.
Pipework, machinery parts (i.e. components requiring some formability or
weldability), vats and bowls,. Greater corrosion resistance to 430.
More corrosive foods (e.g. meat/blood, foods with moderate salt contents)
components, which requires frequently clean, not under excessive stress
and without stationary solids.
Corrosive foods (e.g. hot brine with solids that act as crevice forms,
stagnant and slow moving salty foods).
Corrosive foods (e.g. hot brine in solids, stagnant and also slow
carrying salty foods). Higher strength when compared with austenitics.
High stress corrosion cracking resistance within salt merchandise at
elevated temperatures.
Corrosive foods (e.g. hot brine in solids, that act equally crevice
formers, stagnant in addition to slow taking salty foods). Good stress
at elevated
corrosion cracking resistance within salt merchandise
temperatures. Used in steam heating and hot performs circuits, hot water
boilers, etc.
2.3 Grater blades design.
For soft solid surfaces separating work, the local speed of the material passing through the
cutting blades will be determined by the normal and tangential forces of an element of a
blade material. The ratio of ‘slice’ and ‘push’ velocities, which is defined by ξ. Lower the ξ,
the greater the force reacts at the blade tip and will increase the damage to the cut surfaces.
The forces of reaction also vary depends to the blade curvature which will be discussed in
more details later. The analysis of existing blade design will be concluded to establish a
new design which improves the constraints found [7].
Wherever the intention is, the slicer is made from steel rather from any other materials
and for this case, the circular plate with plural shredding blades formed by bending a small
spaced section up through the plate by a punching form method which create a hole right
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MATEC Web of Conferences 78, 01005 (2016)
DOI: 10.1051/ matecconf/2016 7801005
IConGDM 2016
behind each blade. The shredder will strips the food product into slices where then will pass
through the hole to another side of the plate (to the discharge outlet).
This kind of device (Figure 2) seems to be effective to a soft solid shredding like
vegetable. For a harder solids like meat and bones, it does not suitable and may cause
damage to the machine during operation.
Fig. 2. Rotating Shredder/Slicer Plate [2]
The tougher and heavier duty food shredder blades come in a rotating knife blade form.
This shredder assembly (Figure 3) includes the freeing jams-impact mechanism. This
mechanism stores the energy in its rotating elements which sourced from the driven motor
and being transmitted to the cutting blades which reacts with the materials that are going to
be shredded. The cutting process will continue going to the food reached the desired size of
particles which been determined through the hole size of the screen plates at the bottom of
the chamber. The desired size particles will pass through the screen once meet the size to
the outlet of the machine where the bucket is provided.
Fig. 3. Rotating Shredder/Grater Blade Types [2]
3 Methods and materials
3.1 Properties of food material.
The data of various foods modulus of elasticity, as shown in Table 2 has been collected to
determine the ultimate forces that the grater blades will handle. The variants are from the
soft solid like vegetables and to the hardest possible materials like animal bones. The table
shown next give the values of the specific limits of forces required for varying types of
foods.
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MATEC Web of Conferences 78, 01005 (2016)
DOI: 10.1051/ matecconf/2016 7801005
IConGDM 2016
Table 2. Variety of food material mechanical properties
Food Material
Onions
Modulus of Elasticity, E (MPa)
0.000284
Corn kernels
Apple
Meat
Fish (frozen)
Potato
Wheat
Carrot
Bones
219
0.00014
3.15
0.005
5.2
239
0.004
275.8
3.2 Residual stresses in grater blades.
The material structural components and engineering properties such as distortion, fatigue
life, dimensional stability, the resistance to corrosion and brittle fracture are significantly
influenced by residual stresses [7]. The design process indeed requires to accounting the
residual stress analysis as compulsory to produce the final result of optimum reliability
under actual working conditions. In cyclic loading fatigue (N > 106 cycles), the residual
stresses effect is comparable to the stress concentration effect. Because the residual stresses
do not cause by the loads, it has to be globally balanced and can be expressed in the
equation as follow;
∫ = 0
(1)
3.3 Stress analysis and result.
The development and evaluation of finite element models of grating mechanism for the
cutting and rotating effects will be considered in the thesis. To calculate the original stress,
the finite element analysis and modelling where the displacement boundary conditions
would be the smoothed data attained from the measurements. This data can be easily
described as the input to the finite element modelling.
The theories relate upon the basic assumption that the energy required to produce a
change in its length, dL for a particle of a specific size dimension of L, is given as a simple
power function of L. With the consideration of Kick's and Rittinger’s Law, leads to:
= i (5/2)1/2[1 − (1/q1/2)
(2)
3.4 Finite element analysis modeling.
To visualize the model for the finite element analysis, a simple model of a rotating solid
disc and an annulus with the same dimensions as the grater blade to be analysed. Both the
solid disc and an annulus make the model exactly represent the grater blade. It will also be
modeled asymmetrically with 3-D eighth model. For radial stress calculation, the term can
be defined by such expression;
=
(
)
²
(²²) 1 − ²
where, = poisson ratio for the blade material.
= the mass density of the blade material
5
(3)
MATEC Web of Conferences 78, 01005 (2016)
DOI: 10.1051/ matecconf/2016 7801005
IConGDM 2016
b = disc outer radius
= angular velocity (rad/sec)
= arbitrary radial position
3.5 Rotating solid disc analysis.
Here the illustration the will be applied by open up the hand calculations used for the finite
element analysis results validation, then the parameters and the computer model are shown
and discussed. Finally, the axisymmetric model results will be compared with the hand
calculations. For solid rotating disc, the exact hand calculations are as cited in Boresi and
Schmidt [8]. The hand calculations represent the displacements and stresses of a rotating
solid disc at about its center. Then, the results obtained from these hand calculations are
compared with the results of computer model as an axisymmetric model. The following Eq.
4 is used to define the radial stress, rr, along any arbitrary radial position, r, in a solid disc
rotating about its center.
(4)
()
!" #$
and the arbitrary radial position of the radial displacement is found as the Eq. 5:
%=
&' *
+
$ + -. + -..
(5)
Where -. and -.. area products of integration constants and this is the application for a
solid disc only.
4 Results and discussions
4.1 Nominal dimensions and parameters of a typical cut-off grater/cutting
blade.
There are many dimensions and parameters of a typical cut-off cutting blade which can be
seen in Figure 3. Because the dimensions and parameters can be divided into two criteria,
the parameters are given as:
i) Dimensions of the cutting blade as a whole.
ii) Dimensions of the cutting blade’s rim or outer area.
Fig. 4. Typical nominal parameters of a typical circular cut-off cutting blade
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MATEC Web of Conferences 78, 01005 (2016)
DOI: 10.1051/ matecconf/2016 7801005
IConGDM 2016
Dimensions of the cutting blade as a whole. Cutting Blade as a whole refers to the
Figure 4 above where “A” is the collar diameter. This is where to fix the cutting blade into
the shaft or the arbor of the grating machine. The arbor is a 12 inch length which can fix a
number of 6 blades with a spacer in between of each blade, hexagonal shape as to improve
the driven force to the blade. There are two rows of blades facing each other and the blade
arrangement are alternately in between the opposite blades. Makes the whole area are
included in the cutting mode during the operation. The end of both shafts will be extended
out from the box. This section is to be attached to the gearing mechanism to enable the
same angular velocity for both shafts. But the gearing mechanism and the driver will not be
included in this design as the main objective only focus to the grater mechanism only. The
arrangement of this grater blade only together with the shaft or arbor is as shown in Figure
5.
Fig. 5. The concept of grater blades arrangements
4.2 Grater blade outer area.
It is regarded the outer rim area and it represents the dimensions of the cutting teeth,
gullets, shoulders, cutting teeth pockets, and stop hole radii. Dimension “A” in Figure 4 is
the length of the cutting teeth, measured from a tooth’s bottom side to the outermost point
on the cutting blade. Dimension “B”, is the gullet radius, which brings the meaning of the
radius of the designed area to cope the cutting action dust during the cutting operation and
releasing the dust after that when the cutting tooth passed through the material. Dimension
“C” is the shoulder relief angle. Furthermore, the shoulder relief angle provides the rise to
the dimension “D”, which is the shoulder radius that define the fast dropping off-slope
radius behind the shoulder that leads towards the preceding gullet.
4.3 Axisymmetric model of solid disc.
The results of the radial stress computer axisymmetric-model are shown in Figure 6. Here,
the radial stress is displayed in colours which are defined by the key legend at the top left of
the picture. This is the figure that represents an axisymmetric model of a solid rotating disc
at about its center.
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MATEC Web of Conferences 78, 01005 (2016)
DOI: 10.1051/ matecconf/2016 7801005
IConGDM 2016
Fig. 6. Axisymmetric model showing radial stress (S11) in solid disc.
4.4 Comparing radial stress.
Here, the hand calculated results for the radial stress is to be comparable to the computer
results, the two results did match quite well alike. For the signal-to-noise ratio between the
40 axisymmetric model results and the hand calculations of the radial stress is 3747000 Pa.
Thus, the maximum error for the both results is very low at 9.18E-05 MPa and the error
standard deviation is calculated at 0.0001585 for a maximum stress of 374.7 MPa. These
statistical analysis values are obtained from the hand calculations and the computer results
comparison proves that the computed results are very accurate and extremely well represent
a rotating solid disc. The plots of the results of hand calculation results and the finite
element analysis are as shown in Figure 7.
Fig. 7. The radial and tangential stress in a 4-in (100 mm) radius solid disc
4.5 Comparing radial displacement.
The radial displacement results between the hand calculations and the axisymmetric model
results are compared. The radial displacement signal-to-noise ratio is 117,500 with a
maximum error between the two cases of 3.30E-08 mm and a maximum displacement of
0.004 mm. The estimated error standard deviation is 3.40E-08. As seen in Figure 8, the
solid disc radial displacement of a four inches diameter flats off at its outer edge. The
difference between the axisymmetric results and the hand calculation for radial
displacement on the plot is negligible.
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MATEC Web of Conferences 78, 01005 (2016)
DOI: 10.1051/ matecconf/2016 7801005
IConGDM 2016
Fig. 8. The hand calculation of the radial displacement
4.6 Results of spinning grater blade.
The results obtained from the spinning blade body in Ansys shows the value of stresses
occurred in the model of the solid grater blade disc.. The maximum and minimum stresses
are as seen in the table gives the value of 374.7 MPa and 0.4547 MPa. By comparing these
values to the grater blade material properties, which is given by the 250 MPa. It is assumed
that this grating mechanism could reach the optimum working performance and will not get
failed upon the most extreme food material in its operations. The contour of the equivalent
stress occurs in the solid blade element as in Figure 8, only shows a small gradient of high
stress locating at the center of the bore which is precisely designed in hexagonal shape to
capture the driven inertia force transmitted from the driving device such as motor very
effectively and with high durability.
Fig. 9. The Ansys Elastic Strain Occurred Results of the Model during operations
5 Conclusion
The research overall has resulted in better understanding of a grating blade mechanism.
This paper has given the detail views about the associated stresses that occur in the element.
This will lead to the main objective which to create a new food waste grating device for
home application. The radial stresses acting to the model is that obtained through computer
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MATEC Web of Conferences 78, 01005 (2016)
DOI: 10.1051/ matecconf/2016 7801005
IConGDM 2016
analysis then compared to another method of hand calculation to see its discrepancies as
well to validate the results.
The study conducted is able to compare the most suitable material and geometric shape
of the grating blades by comparing with similar existing devices in the market. The
proposed material and blade design have evaluated their characteristics and performance by
using the FEM method. By taking all constraints regarding the design as well as its
advantages are to be considered in designing, a new grating blade for the optimum multiangle end product is able to be proved. The problem of solid disc that associates with the
rotation and cutting loads, the length of the specimen to be cut and the residual stress has
also been solved in this research.
This work was financially supported by the Universiti Malaysia Perlis Seed Money (9014-00034).
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5. P.W. Jeffrey, Designing an Appropriate Technology Shredder in a Developing
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